This invention relates to a process for purification of technical grade pentachlorophenol in order to obtain high-purity pentachlorophenol which is adapted for use as an active ingredient in agricultural chemicals or industrial antiseptics that are free from pollution problems.
Pentachlorophenol is industrially manufactured by the chlorination of phenol, but the technical grade of pentachlorophenol obtained in this way contains as impurities various phenolic acid substances and non-phenolic neutral substances.
Among these impurities are chlorodibenzodioxines or chlorodibenzofurans that are known to be strongly toxic, and substances that are said to be the precursors of these compounds, such as for example, chlorodiphenyl ethers, chlorophenoxyphenols, and chlorodihydroxybiphenyls, so that in the application of technical grade pentachlorophenol to agricultural chemicals or industrial antiseptics that are free from pollution problems it was eagerly desired to remove the above described harmful impurities, but at present no effective method for the removal of these impurities has yet been established.